CN115085579A - Vibration actuator and optical device with reduced size and suppressed generation of abnormal noise - Google Patents

Abstract

A vibration actuator and an optical device are provided which are miniaturized while suppressing generation of abnormal noise. The vibration actuator includes: a vibration element having a piezoelectric element and an elastic member; and a contact body that contacts the vibration element. The contact body has a square bar shape whose width and thickness are substantially uniform in the longitudinal direction with a direction in which the vibrating element and the contact body move relative to each other as the longitudinal direction, and includes a first section and a second section in a region where the vibrating element is frictionally slid, the first section and the second section being formed with R surfaces having different radii of curvature, respectively, at edges extending in the longitudinal direction.

Description

Vibration actuator and optical device with reduced size and suppressed generation of abnormal noise

Technical Field

The invention relates to a vibration actuator and an optical apparatus.

Background

The vibration type actuator has a characteristic capable of generating a large thrust and capable of positioning with high accuracy, has excellent quietness, and is widely used, for example, to drive a focus lens or an image blur correction lens of an image pickup apparatus. Further, in recent years, a vibration type actuator is used as a driving source of a pan driving device or a tilt driving device for monitoring a lens of a camera or a web camera.

The vibration actuator is a driving device as follows: the thrust force (driving force) is generated by bringing the vibrating element and the contact body into frictional contact with each other to excite a predetermined vibration in the vibrating element and moving the vibrating element and the contact body relative to each other. Therefore, when the vibration type actuator is driven, unnecessary vibration is sometimes generated in the contact body due to vibration excited in the vibration element, and the unnecessary vibration generated in the contact body sometimes causes abnormal noise. Therefore, it is desirable to prevent unnecessary vibration from being generated in the contact body when driving the vibration actuator.

In order to suppress the generation of vibration in the contact body, in most cases, the vibration actuator is designed to prevent the driving frequency of the vibrating element and the resonance frequency of the contact body from coinciding with each other. However, for example, a contact body as a component of a linear drive type vibration actuator generally has not only typical vibrations such as out-of-plane vibrations, in-plane vibrations, torsional vibrations, and the like, but also various natural vibration modes (resonant vibration modes) specific to its shape. In order to solve this problem, japanese patent laid-open No.2018-67983 has proposed a vibration actuator (vibration motor) designed such that the frequency of a contact body in all natural vibration modes is far from a driving frequency by a predetermined value or more.

There is a strong need for: the vibration actuator is required not only to suppress the generation of the above-described abnormal noise but also to be downsized and lightened. To meet this requirement, for example, in the case of reducing the thickness of the contact body, generally the resonance frequency of the contact body in the natural vibration mode is shifted to the lower frequency side, and the frequency interval between adjacent frequency steps (orders of frequency) is reduced (narrowed). As a result, it is difficult to design the vibration actuator so that all natural vibration modes in the vicinity of the driving frequency are located outside the driving frequency band of the vibration element, so that there may occur a situation where unnecessary vibrations are excited in the contact body under specific driving conditions, resulting in generation of abnormal noise in the audible range.

Disclosure of Invention

The invention provides a vibration actuator which can realize miniaturization and restrain abnormal noise generation, and an optical device comprising the vibration actuator.

In a first aspect of the present invention, there is provided a vibration actuator comprising: a vibration element including an electromechanical energy conversion element and an elastic member; and a contact body that is in contact with the vibration element, the contact body having a direction in which the vibration element and the contact body move relative to each other as a longitudinal direction, the contact body having a square bar shape whose width and thickness are substantially uniform in the longitudinal direction, and the contact body including a first section and a second section in a region where friction sliding is performed on the vibration element, the first section and the second section being formed with R surfaces having different radii of curvature, respectively, at edges extending in the longitudinal direction.

In a second aspect of the present invention, there is provided a vibration actuator comprising: a vibration element including an electromechanical energy conversion element and an elastic member; and a contact body that is in contact with the vibrating element, the contact body having an annular shape whose width in a radial direction and thickness in an axial direction are substantially uniform, a surface parallel to the radial direction is a frictional sliding surface that frictionally slides on the vibrating element, and the contact body includes a first section and a second section, each of which has an R surface formed on an outer peripheral edge with a different radius of curvature.

In a third aspect of the present invention, there is provided an optical apparatus comprising: a vibration actuator; and an optical component driven by the vibration actuator, the vibration actuator including: a vibration element including an electromechanical energy conversion element and an elastic member; and a contact body that is in contact with the vibration element, the contact body having a direction in which the vibration element and the contact body move relative to each other as a longitudinal direction, the contact body having a square bar shape whose width and thickness are substantially uniform in the longitudinal direction, and the contact body including a first section and a second section in a region where friction sliding is performed on the vibration element, the first section and the second section being formed with R surfaces having different radii of curvature, respectively, at edges extending in the longitudinal direction.

In a fourth aspect of the present invention, there is provided an optical apparatus comprising: a vibration actuator; and an optical component driven by the vibration actuator, the vibration actuator including: a vibration element including an electromechanical energy conversion element and an elastic member; and a contact body that is in contact with the vibrating element, the contact body having an annular shape whose width in a radial direction and thickness in an axial direction are substantially uniform, a surface parallel to the radial direction is a frictional sliding surface that frictionally slides on the vibrating element, and the contact body includes a first section and a second section, each of which has an R surface formed on an outer peripheral edge with a different radius of curvature.

According to the present invention, a vibration actuator that suppresses generation of abnormal noise while achieving miniaturization, and an optical apparatus including the vibration actuator can be obtained.

Further features of the invention will become apparent from the following description of exemplary embodiments (with reference to the accompanying drawings).

Drawings

Fig. 1A to 1D are diagrams illustrating an overall configuration of a linear driving type vibration actuator.

Fig. 2A to 2C are diagrams for explaining the vibration form of the contact body in a typical natural vibration mode.

Fig. 3A to 3C are diagrams for explaining the structure of a contact body used in the vibration actuator according to the first embodiment.

Fig. 4A and 4B are graphs for explaining respective natural vibration modes of the contact body appearing in fig. 1A to 1D and the contact body shown in fig. 3A to 3C.

Fig. 5 is a schematic diagram showing a torsional vibration pattern having three peaks (crest) of the contact body shown in fig. 3A to 3C.

Fig. 6A to 6C are diagrams illustrating a modification of the contact body illustrated in fig. 3A to 3C.

Fig. 7 is a graph for explaining a change in resonance frequency in the natural vibration mode caused in the case of using the contact body shown in fig. 6A to 6C.

Fig. 8A and 8B are diagrams for explaining the structure of a contact body used in the vibration actuator according to the second embodiment.

Fig. 9A to 9F are diagrams for explaining the vibration patterns of the contact body shown in fig. 8A and 8B in a typical natural vibration mode.

Fig. 10A to 10C are diagrams illustrating the overall configuration of the lens driving device.

Fig. 11 is an exploded perspective view showing the overall configuration of the pan/tilt head drive device.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings showing embodiments of the invention. The vibration actuators according to embodiments of the present invention have significant features in terms of the structure of the contact body, compared to vibration actuators according to the prior art, but on the other hand, the vibration actuators can be formed without substantial differences in other components of the construction. Therefore, first, a description will be given of an example of a known configuration of the vibration actuator, and then a contact body as a characteristic component of the vibration actuator according to each embodiment of the present invention will be described.

Fig. 1A and 1B are exploded perspective views of the linear drive type vibration actuator 1, and fig. 1A and 1B are different from each other in a direction of viewing elements (components) of the vibration actuator 1. Fig. 1C is a front view of the vibration actuator 1, and fig. 1D is a side view of the vibration actuator 1.

To explicitly show the correspondence between the drawings, and further, for convenience of explanation, an X axis (X direction), a Y axis (Y direction), and a Z axis (Z direction) orthogonal to each other are defined as shown in fig. 1A to 1D. When describing the components of the vibration actuator 1, directions indicated by the X direction, the Y direction, and the Z direction will be explained, respectively.

The vibration actuator 1 includes a vibration element 11, a contact body 12, a holding member 13, a pressing member 14, a guided member 15, a fixing member 16, a screw 17, and a rolling member 18. As an example of the electromechanical energy conversion element, the vibration element 11 has a rectangular plate-shaped elastic member 112 and a rectangular plate-shaped piezoelectric element 111. Two surfaces of the elastic member 112 facing the thickness direction (Z direction), that is, one of two planes perpendicular to the Z direction, is bonded (bond) with the piezoelectric element 111, and the other is formed with two protrusions 112a protruding toward the contact body 12 with a predetermined spatial interval in the X direction. In addition, opposite ends of the elastic member 112 in the longitudinal direction (X direction) are provided with held portions 112b extending outward (in the ± X direction), respectively.

For example, the piezoelectric element 111 is formed of piezoelectric ceramics of lead zirconate titanate (PZT), and the elastic member 112 is formed of metal such as stainless steel. By applying an AC voltage of a predetermined frequency to the piezoelectric element 111, vibration of a predetermined vibration mode can be excited in the vibration element 11, thereby causing the tip of the protrusion 112a to make an elliptical motion. Note that a mechanism for generating an elliptical motion at the tip of the protrusion 112a is known, and thus a detailed description is omitted here.

The held portion 112b is adhesively fixed to the holding member 13. Thus, the vibration element 11 is held by the holding member 13, thereby preventing excitation of vibration from being suppressed. The pressing member 14 is, for example, a plate spring, and the projection 112a is brought into pressure contact with the contact body 12 by pressing the holding member 13 toward the contact body 12 with a reaction force generated by elastic deformation. The guided member 15 sandwiches the pressing member 14 between it and the holding member 13, thereby elastically deforming the pressing member 14.

The guided member 15 is formed with two guide grooves 15a extending in the driving direction (X direction) of the vibration actuator 1. The fixed member 16 is formed with two guide grooves 16a extending in the X direction such that the guide grooves 16a are opposed to the two guide grooves 15a of the guided member 15 in the Z direction.

The contact 12 has a square bar shape whose longitudinal direction is the X direction and whose width (length in the Y direction) orthogonal to the longitudinal direction is larger than its thickness (length in the Z direction). Note that, as will be described later, the longitudinal direction of the contact body 12 is a direction in which the vibration element 11 and the contact body 12 move relative to each other.

Respective portions of the contact body 12 near both opposite ends in the longitudinal direction are formed with holes penetrating in the thickness direction (Z direction). A screw 17 (fastening member) is inserted through a hole formed in the contact body 12 and fastened to the fixing member 16, thereby fixing the contact body 12 to the fixing member 16. A cross section of the contact body 12 taken along a plane (Y-Z plane) orthogonal to the longitudinal direction (X direction) is uniform in the longitudinal direction.

Rolling members 18 (balls), each having a spherical shape, are sandwiched between a guide groove 15a formed in the guided member 15 and a guide groove 16a formed in the fixed member 16, whereby the guided member 15 is held to the fixed member 16 in such a manner that the guided member 15 can move only in the X direction.

In the vibration type actuator 1, when a predetermined vibration is excited in the vibration element 11 to cause the projection 112a to make an elliptical motion in the Z-X plane, a driving force for moving the vibration element 11 and the contact 12 relative to each other in the X direction is generated at the contact surface between the projection 112a and the contact 12. This causes the vibration element 11, the holding member 13, the pressing member 14, and the guided member 15 to move in unison in the X direction, which is the driving direction, with respect to the contact body 12 and the fixed member 16.

Fig. 2A to 2C are diagrams for explaining the vibration patterns of the contact body 12 in a typical natural vibration mode. Fig. 2A schematically shows the out-of-plane bending vibration of the contact body 12 having an amplitude in the thickness direction (Z direction). Fig. 2B schematically shows in-plane bending vibration of the contact body 12 having an amplitude in the width direction (Y direction). Fig. 2C schematically shows torsional vibration having a torsional amplitude about an axis in the longitudinal direction of the contact body 12 as the rotation axis. Here, although resonance modes in which the resonance frequencies are all smallest in the associated vibration patterns, that is, resonance modes each having one vibration peak are shown as a representative, there is a natural vibration mode of higher-order frequencies (high order of frequency) each having a plurality of peaks on the frequency side higher than the illustrated frequency.

Next, a vibration actuator according to a first embodiment of the present invention will be described. The vibration actuator according to the first embodiment is different from the vibration actuator 1 shown in fig. 1A to 1D in that, as a component of the vibration actuator 1, a contact body 30 or a contact body 30A described later is included instead of the contact body 12. Therefore, a description will be given mainly about the configuration of the contact bodies 30 and 30A below.

Fig. 3A to 3C are diagrams for explaining the structure of a contact 30 used for the vibration actuator according to the first embodiment of the present invention. More specifically, fig. 3A is an external perspective view of the contact body 30. Note that, similarly to the contact body 12, the length direction, the width direction, and the thickness direction of the contact body 30 are also defined as the X direction, the Y direction, and the Z direction, respectively. Like the contact body 12, the contact body 30 has a square bar shape with substantially uniform width and thickness.

Opposite ends in the longitudinal direction (X direction) of the contact body 30 are formed with fixing portions 32 for fastening the contact body 30 to the fixing member 16 with screws 17, and a friction portion 31 is formed between the fixing portions 32 formed at the opposite ends in the longitudinal direction. One of the front and back surfaces (surfaces orthogonal to the Z direction (along the X-Y plane)) of the friction portion 31 forms a frictional sliding surface associated with the protrusion 112a of the vibration element 11.

The friction portion 31 has a first section and a second section having R surfaces formed at two edges on the front surface side (+ Z side) among four edges extending in the length direction of the contact body 30 such that the radius of curvature of the R surface of the first section is different from that of the R surface of the second section. The first section is provided at substantially the center of the friction portion 31 in the longitudinal direction, and the two second sections are provided so as to sandwich the first section in the longitudinal direction.

Fig. 3B is a Y-Z sectional view (a view showing a section orthogonal to the X direction) of the first section of contact body 30. Fig. 3C is a Y-Z cross-sectional view of the second section of contact body 30. Of the four edge portions extending in the longitudinal direction of the contact body 30, two edge portions located on the back surface side (-Z side) are not different in shape from the first section. On the other hand, of the four edge portions of the contact body 30 extending in the longitudinal direction, the radius of curvature of the R-surface of the first section is relatively larger than the radius of curvature of the R-surface of the second section, on the two edge portions located on the front surface side (+ Z side). That is, the first section is formed with R-faces each having a radius of curvature relatively larger than that of the R-face of the second section. The R-face can be formed by R-face rounding (including any of cutting, grinding, lapping, and the like). In the case of molding the contact body 30 by casting, the R-face can also be formed by using a mold.

Each R-face of the first segment is formed in the following region: this region extends from the edge located on the front surface side (X-Y plane side) by a length of 1/4 not more than the width B of the contact body 30 (friction portion 31) and from the edge located on the side surface side (Z-X plane side) by a length of 1/2 not more than the thickness T of the contact body 30 (friction portion 31). The amount of the portion of the first section removed by R rounding is configured to be no greater than the maximum amount assumed to be removed by C rounding under the limitation of the above dimensional range.

Note that the edges of the contact body 30, at which the first section and the second section can be provided, are limited to four edges extending in the length direction. Although in the contact body 30, the R surfaces having different radii of curvature are provided at the two edges on the front surface side, the R surfaces having different radii of curvature may be provided at the two edges on the back surface side. Further, the R-faces having different radii of curvature may be provided at all four edges extending in the length direction. Further, although in the contact body 30, the R surface having a large radius of curvature is provided only at one portion of each edge located on the front surface side, the R surface having a large radius of curvature is not limited to be provided at one portion, but can be provided at a plurality of portions (more specifically, two or four portions). Further, although in the contact body 30, the radius of curvature of the R-face is uniform in the first section, the radius of curvature of the R-face may vary in the length direction in the first section. The length in the length direction of the first section of the contact 30 is limited, which will be described later.

The fixing portions 32 are portions for fixing the contact body 30 to the fixing member 16 with screws 17, and are each in the form of a U-shaped groove. The screw 17 is inserted through the U-shaped groove in the thickness direction and fastened to the fixing member 16, thereby fixing the contact 30 to the fixing member 16. The contact 30 is a structural body formed such that the fixing portions 32 and the friction portions 31 are continuous with each other with the same thickness and the same width, but the thickness and shape of each fixing portion 32 are not limited thereto. For example, the thickness and width of each fixing portion 32 may be different from those of the friction portion 31, a through hole may be provided instead of the U-shaped groove similarly to the contact body 12, and further, the fixing may be achieved by other means than the screw 17.

Next, the technical effect provided by the contact body 30 having the first section will be described. Fig. 4A is a graph for explaining the natural vibration mode of the contact body 12. Fig. 4B is a graph for explaining the natural vibration mode of the contact body 30. In fig. 4A and 4B, the horizontal axis represents the number of peaks in the three vibration modes (out-of-plane vibration, in-plane vibration, and torsional vibration) described with reference to fig. 2A to 2C, and the vertical axis represents the resonance frequency in each natural vibration mode. Note that only three vibration modes, that is, out-of-plane vibration, in-plane vibration, and torsional vibration are considered, because in the rod-shaped contact bodies 12 and 30 each having four edges in the length direction, the vibration mode to be considered that appears in the low frequency band is narrowed down to these three types.

It is known that in a beam having a fixed length, the resonance frequency becomes higher as the number of peaks increases, and therefore, with the contact bodies 12 and 30, the resonance frequency becomes higher as the number of peaks in each vibration mode of out-of-plane vibration, in-plane vibration, and torsional vibration increases.

The contact body 12 does not have a section corresponding to the first section provided in the contact body 30. Therefore, as shown in fig. 4A, the resonance frequency in the vibration mode of torsional vibration (resonance frequency of vibration having three peaks) is included in the drive frequency band of the vibration element 11. On the other hand, since contact body 30 is provided with the first section including the R face formed to have a large radius of curvature, the resonance frequency of torsional vibration having three peaks may be shifted out of the drive frequency band of vibration element 11 toward the higher frequency side.

Here, as is clear from comparison between fig. 4A and 4B, the resonance frequency of the out-of-plane vibration hardly changes, and further, the resonance frequency of the in-plane vibration changes only slightly. Therefore, by providing the first section in the contact body, the resonance frequency of the torsional vibration can be selectively moved away from the drive frequency band of the vibrating element 11, with the result that the generation of abnormal noise can be suppressed when the vibration type actuator is driven.

The reason why the resonance frequency of the in-plane vibration and the out-of-plane vibration hardly changes but the resonance frequency of the torsional vibration largely changes will be described with reference to fig. 5. Fig. 5 is a schematic diagram showing a torsional vibration pattern of contact body 30 having three peaks. The top of the peak of the torsional vibration is present in the first section of contact body 30. At this time, the mass of the peak of the torsional vibration may reduce the amount of the portion of the edge portion removed by forming the R-face having a large radius of curvature in the first section, which causes the resonance frequency to become high. In addition, the top of the peak of the torsional vibration having one peak is also present in the first section. Therefore, the resonance frequency of the torsional vibration having one peak also becomes high. That is, by providing the first section in which the R surface having a large radius of curvature is formed in the contact body 30, the resonance frequency of the torsional vibration having odd-numbered peaks is increased.

On the other hand, in the case where the torsional vibration has an even number of peaks, a node (node) of the torsional vibration exists in the first section. At this time, due to the R-face having a large radius of curvature provided in the first section, a portion of the torsional vibration that undergoes large distortion is eliminated, so that the resonance frequency of the torsional vibration having an even number of peaks becomes low. In other words, the first section is away from the neutral axis of torsional vibration, which has a significant effect on the geometrical moment of inertia, and therefore the resonance frequency is lowered by an amount corresponding to the mass eliminated by providing the R-face with a large radius of curvature.

Next, the limitation of the length in the length direction of the first section will be described. In the case where the first section is provided at the position of an antinode (anti) of vibration, this provides an effect of shifting the resonance frequency of vibration to a higher frequency side. Therefore, it is necessary to set the length in the length direction of the first section to a length between nodes of vibration having the following frequency order (i.e., a length of 1/2 not greater than the wavelength): the resonant frequency of the frequency order is to be outside the drive band. In the contact body 30, it is desirable to set the length in the length direction of the first section to a length not greater than 1/2, which has the wavelength of the torsional vibration of three peaks.

Note that, for out-of-plane vibration and in-plane vibration, a portion that undergoes large distortion is partially eliminated due to the provision of the first section formed with the R-face having a large radius of curvature, and thus the resonance frequency changes in the same mechanism as that of torsional vibration. However, the effect of the first section on the geometrical moment of inertia is very small under out-of-plane and in-plane vibrations.

As described above, in contact body 30, by providing the first section in which the R-face having a large radius of curvature is formed in the edge extending in the longitudinal direction, the resonance frequency of the torsional vibration can be controlled without affecting the resonance frequencies of the out-of-plane vibration and the in-plane vibration. Therefore, the resonance frequency of the torsional vibration can be shifted out of the drive frequency band of the vibration element 11, and thus the generation of abnormal noise can be suppressed.

Next, a modification of the contact body 30 will be described. Fig. 6A to 6C are diagrams for explaining the structure of the contact 30A. Fig. 6A is an external perspective view of contact body 30A. Fig. 6B is a Y-Z cross-sectional view of the first section of contact body 30A. Fig. 6C is a Y-Z cross-sectional view of the second section of contact body 30A.

The contact body 30A is different from the contact body 30 in that a step S is provided in such a manner as to narrow the width of the first section, but the other configuration is the same as that of the contact body 30. Therefore, in fig. 6A to 6C, the first section is clearly illustrated, and reference numerals of other portions are omitted. A description will be given mainly of the first section having the step S.

The side surface of the first section is formed with a corresponding step by being removed by a certain depth in the Y direction, thereby making the width of the first section narrower than that of the second section. Further, the first section is formed with R surfaces each having a radius of curvature larger than that of the R surface of the second section in a range where the step S is provided in the longitudinal direction.

Fig. 7 is a graph for explaining a change in resonance frequency in the natural vibration mode caused in the case of using the contact body 30A for the vibration actuator. In fig. 7, the resonance frequencies of the contact not formed with the first section (contact having the same structure as the contact 12 shown in fig. 1A to 1D) at the respective vibration modes are plotted. Here, the resonance frequencies of the torsional vibration and the in-plane vibration each having two peaks are included in the drive frequency band. In the description with reference to fig. 4A and 4B, the influence of the geometrical moment of inertia of the R-plane internal vibration having a large radius of curvature is very small. On the other hand, in contact body 30A, due to the step S provided in the side surface in the width direction, the portion that undergoes large distortion is uneven, which has a significant effect on the geometrical moment of inertia in the in-plane vibration mode to shift the resonance frequency of the in-plane vibration to the lower frequency side. Therefore, by shifting the resonance frequency of the in-plane vibration having two peaks to the lower frequency side, the resonance frequency can be shifted out of the drive frequency band, and this state is indicated by the arrow in fig. 7.

Therefore, by providing the first section, the resonance frequency of the torsional vibration and the in-plane vibration can be selectively shifted outside the drive frequency band, and as a result, the generation of abnormal noise can be suppressed. Note that although in the contact body 30A, the width of the first section is made narrower than the width of the second section by providing the step S, conversely, the resonance frequency of the torsional vibration and the in-plane drive can also be selectively moved outside the drive frequency band by making the width of the first section larger than the width of the second section.

Next, a description will be given of a contact body for a vibration actuator according to a second embodiment of the present invention. The vibration actuator according to the second embodiment is a vibration actuator that performs rotational driving as described later with reference to fig. 11, and includes a contact body having an annular shape. The general configuration of the vibration actuator according to the second embodiment will be described later with reference to fig. 11, where the structure of the contact body having an annular shape will be described in detail.

Fig. 8A is an external perspective view of a contact 60 for a vibration actuator according to a second embodiment of the present invention. The contact body 60 has an annular shape, and has an inner peripheral portion and an outer peripheral portion which are different in thickness. The inner peripheral portion of the contact body 60 is a portion for connection with a rotating body, not shown, and is smaller in thickness than the outer peripheral portion. The outer peripheral portion has a thickness T and a width B in the radial direction, and one of the front and back surfaces parallel to the radial direction forms a frictional sliding surface that slides on the vibrating element 11 (not shown).

The outer periphery of the contact body 60 is formed with a plurality of first segments at equal intervals in the circumferential direction, and portions between adjacent first segments form second segments. The first segment is a segment having an outer peripheral edge formed with an R-face having a large radius of curvature, and the second segment is a segment having an outer peripheral edge formed with an R-face having a radius of curvature relatively smaller than the radius of curvature of the R-face of the first segment. Fig. 8B is a cross-sectional view taken along a-a in fig. 8A, showing a cross-section of the first section. The contact 60 has an R-face with a large radius of curvature provided on the outer peripheral edge of both the front and rear faces. Note that the edge on which the R-face having a large radius of curvature can be formed is not limited to the outer peripheral edges of the front and back surfaces, and the R-face is not formed on the edge of the outer peripheral portion on the inner peripheral side. Here, although the R-face having a large radius of curvature is provided on the outer peripheral edges of both the front surface side and the back surface side, the R-face may be formed on one of the outer peripheral edges.

As shown in fig. 8B, the R-face in each first section of the contact 60 is formed in the following region: this region extends from the associated edge by a length of no more than 1/4 of the width B of the contact body 60 on both the front and back sides, and from the associated outer edge by a length of no more than 1/2 of the thickness T of the contact body 60 on the outer peripheral side. The amount of the portion of the first section removed by R rounding is configured to be no greater than the maximum amount assumed to be removed by C rounding under the limitation of the above dimensional range. Other configurations of the first section are similar to those of the contact body 30, and thus a description thereof is omitted.

Fig. 9A to 9F are diagrams for explaining the vibration patterns of the contact body 60 in a typical natural vibration mode. Fig. 9A and 9B are diagrams schematically illustrating out-of-plane bending vibration of the contact body 60 having an amplitude in the axial direction. Fig. 9C and 9D are diagrams schematically illustrating in-plane bending vibration of the contact body 60 having an amplitude in the radial direction. Fig. 9E and 9F are diagrams schematically showing torsional vibration having a torsional amplitude about the rotation axis in the circumferential direction of the contact body 60. Here, although fig. 9A to 9F show resonance modes each having six vibration peaks by way of a typical example, there are natural vibration modes having different numbers of peaks on the lower frequency side and the higher frequency side.

The vibration mode of the contact body 60 is characterized in that generally even a vibration mode having the same number of peaks includes two modes called a sin mode and a cos mode. One of the modes has a peak top position in the first section and the other mode has a node position in the first section. At this time, the former reduces the mass at the peak position, and thus makes the resonance frequency of the torsional vibration higher. Conversely, the latter has a portion that undergoes large distortion location cancellation, which lowers the resonance frequency of the torsional vibration. Therefore, a difference occurs between the resonance frequencies in the sin mode and the cos mode of the torsional vibration mode having the same number of peaks.

In a vibration actuator that frictionally drives an annular contact body, it is known that abnormal noise is generated by exciting a traveling wave (traveling wave) of a specific vibration mode in the contact body. On the other hand, in contact body 60, since a difference occurs in resonance frequency between the sin mode and the cos mode of the traveling wave, the generation of the traveling wave is not caused by the vibration energy from the vibration element, and as a result, the generation of abnormal noise can be suppressed. Note that the formation of the R-face having a large radius of curvature has no significant influence on the resonance frequency in both vibration modes of the out-of-plane vibration and the in-plane vibration for the same reason as that of the contact body 30.

Therefore, in the annular contact body 60, by providing the first sections each having the R-face with a large radius of curvature at the outer peripheral edge, the resonance frequency of the torsional vibration can be controlled without substantially affecting the out-of-plane vibration and the in-plane vibration. As a result, generation of abnormal noise can be suppressed.

Next, an example of an optical device using the vibration actuator will be described. Fig. 10A is a diagram showing the overall configuration of the lens driving device 40. Fig. 10B is a front view of the lens driving device 40. Fig. 10C is a side view of the lens driving device 40.

The lens driving device 40 shown in fig. 10A to 10C uses the same vibration actuator as the vibration actuator 1 shown in fig. 1A to 1D in terms of function, and thus uses the same reference numerals and detailed description is omitted. Fig. 10A to 10C show the configuration of the lens driving device 40 in a simplified manner. The lens driving device 40 includes the vibration actuator 1, an optical lens 41 (optical component), a lens holding member 42, and a guide member 43.

The optical lens 41 is, for example, a focus lens used in a lens barrel of the image pickup apparatus. The lens holding member 42 holds the optical lens 41. The guide members 43 are inserted through holes formed in the lens holding member 42, and in this state, opposite ends of each guide member 43 are fixed within the lens barrel substantially in parallel with the optical axis O of the optical lens 41. Thereby, the optical lens 41 is guided by the guide member 43 so that the optical lens 41 can move in the optical axis direction.

The lens holding member 42 is provided with a fitting portion 42 b. Further, the guided member 15 of the vibration actuator 1 is provided with a fitting projection 15b that is fitted in the fitting portion 42 b. The fixing member 16 is fixed at a predetermined position within the lens barrel such that the fitting projection 15b is fitted in the fitting portion 42b and the moving direction of the guided member 15 is substantially parallel to the optical axis O. Therefore, by driving the vibration actuator 1 to move the guided member 15 in the optical axis direction, the optical lens 41 can be moved in the optical axis direction.

In the lens barrel equipped with this lens driving device 40, there is a strong demand for miniaturization of the vibration actuator in order to achieve miniaturization of the lens barrel. As described above, since the resonance frequency of the contact body in the natural vibration mode enters the drive frequency band, the miniaturization of the vibration actuator may cause generation of abnormal noise in the audible range. In order to solve this problem, the above-described structure of the contact body 30 is applied to the contact body as a component of the vibration actuator, whereby it is possible to achieve miniaturization of the vibration actuator by making the contact body thinner and smaller while suppressing generation of abnormal noise.

Fig. 11 is an exploded perspective view of a pan/tilt driving device (pan/tilt driving device)50 using a vibration actuator. The image pickup unit 57 supports a lens barrel 58 incorporating optical components such as various lenses and diaphragms, so that the lens barrel 58 can rotate about the pitch rotation axis TL. The imaging unit 57 is a driven member of the pan and tilt head driving device 50, and is supported by an intermediate cover 59 so that the imaging unit 57 can rotate about the pan rotation axis PN in unison with the lens barrel 58. The connecting member 56 is connected with the contact 60 with the screw 55, whereby the contact 60 and the image pickup unit 57 are connected with each other. The intermediate cover 59 is fixed to the base 54.

In fig. 11, the entire configuration of the vibration actuator 1 is not shown. The vibration actuator 1 is held by an actuator support plate 51, and the actuator support plate 51 is fixed to a base 54. Two protrusions 112a of the vibration element 11 are in contact with the surface on the-Y side of the contact body 60. The driving force of the vibration actuator acts in the tangential direction of the contact body 60 to rotate the contact body 60 about the pan rotation axis PN, thereby also rotating the image pickup unit 57 about the pan rotation axis PN. The contact 60 holds the scale 53 for position detection. The scale 53 is disposed on the surface opposite to the position detection sensor 52 fixed to the actuator support plate 51, and the rotation angle of the contact body 60 can be determined by the position detection sensor 52. Note that as an actuator for driving the lens barrel 58 to rotate about the pitch rotation axis TN, an actuator equivalent to an actuator for rotating the image pickup unit 57 about the pan rotation axis PN can be used.

In the pan/tilt head driving device 50, it is also possible to achieve miniaturization of the vibration actuator while suppressing generation of abnormal noise for the same reason as that of the lens driving device 40.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims priority from Japanese patent application No.2021-031805, filed 3/1/2021, which is hereby incorporated by reference in its entirety.

Claims (16)

1. A vibration actuator comprising:

a vibration element including an electromechanical energy conversion element and an elastic member; and

a contact body that is in contact with the vibration element,

characterized in that the contact body has a square bar shape with a width and a thickness substantially uniform in the longitudinal direction with a direction in which the vibrating element and the contact body move relative to each other as the longitudinal direction, and includes a first section and a second section in a region in which the vibrating element is frictionally slid, the first section and the second section being formed with R surfaces having different radii of curvature, respectively, at edges extending in the longitudinal direction.

2. The vibration actuator of claim 1 wherein the radius of curvature of the first section is greater than the radius of curvature of the second section, the first section being disposed at a location corresponding to an antinode or a node of the contact in the torsional vibration mode.

3. The vibratory actuator of claim 2, wherein the contact has a plurality of the first sections.

4. The vibration actuator of claim 2, wherein the length of the first section in the direction in which the contact moves relative to the vibrating element is no greater than 1/2 of the wavelength in the torsional vibration mode closest to the order of the drive frequency band of the vibrating element.

5. The vibration actuator of claim 4, wherein the width of the first section is less than the width of the second section.

6. The vibration actuator according to claim 5, wherein in the first section, a length of a region where the R face is formed is shorter than a length of a region having a width smaller than that of the second section in a direction in which the contact moves relative to the vibration element.

7. The vibration actuator according to claim 1, wherein in a cross section orthogonal to a direction in which the contact body moves relative to the vibration element, the R-face in the first section is formed in a region in which: the region extends from the edge over a length no greater than 1/4 of the width on a surface parallel to the width direction and extends from the edge over a length no greater than 1/2 of the thickness on a surface parallel to the thickness direction.

8. A vibration actuator comprising:

a vibration element including an electromechanical energy conversion element and an elastic member; and

a contact body that is in contact with the vibration element,

characterized in that the contact body has an annular shape having a substantially uniform width in the radial direction and thickness in the axial direction, a surface parallel to the radial direction is a frictional sliding surface that frictionally slides on the vibrating element, and the contact body includes a first section and a second section each having an R surface formed on an outer peripheral edge with a different radius of curvature.

9. The vibration actuator according to claim 8, wherein a radius of curvature of the first section is larger than a radius of curvature of the second section, the first section being provided at a position corresponding to an antinode or a node of the contact in the torsional vibration mode.

10. The vibratory actuator of claim 9, wherein the contact body has a plurality of first sections.

11. The vibration actuator of claim 9, wherein the length of the first section in the direction in which the contact moves relative to the vibrating element is no greater than 1/2 of the wavelength in the torsional vibration mode closest to the order of the drive frequency band of the vibrating element.

12. The vibration actuator of claim 11, wherein the width of the first section is less than the width of the second section.

13. The vibration actuator according to claim 12, wherein in the first section, a length of a region where the R-face is formed is shorter than a length of a region having a width smaller than that of the second section in a direction in which the contact moves relative to the vibration element.

14. The vibration actuator according to claim 8, wherein in a cross section orthogonal to a direction in which the contact body moves relative to the vibration element, the R-face in the first section is formed in a region in which: the region extends from the edge over a length no greater than 1/4 of the width on a surface parallel to the width direction and extends from the edge over a length no greater than 1/2 of the thickness on a surface parallel to the thickness direction.

15. An optical device, comprising:

a vibration actuator; and

an optical component driven by the vibration actuator,

the vibration actuator includes:

a vibration element including an electromechanical energy conversion element and an elastic member; and

a contact body that is in contact with the vibration element,

characterized in that the contact body has a square bar shape with a width and a thickness substantially uniform in the longitudinal direction with a direction in which the vibrating element and the contact body move relative to each other as the longitudinal direction, and includes a first section and a second section in a region in which the vibrating element is frictionally slid, the first section and the second section being formed with R surfaces having different radii of curvature, respectively, at edges extending in the longitudinal direction.

16. An optical device, comprising:

a vibration actuator; and

an optical component driven by the vibration actuator,

the vibration actuator includes:

a vibration element including an electromechanical energy conversion element and an elastic member; and

a contact body that is in contact with the vibration element,

characterized in that the contact body has an annular shape having a substantially uniform width in the radial direction and thickness in the axial direction, a surface parallel to the radial direction is a frictional sliding surface that frictionally slides on the vibrating element, and the contact body includes a first section and a second section each having an R surface formed on an outer peripheral edge with a different radius of curvature.

Images